Apparatus for detecting open circuits in parallel-wired thermo modules

1. An apparatus for detecting an open circuit in parallel-wired thermo modules characterized in that the apparatus comprises: a group of thermo modules including plural rows of plural series-connected thermo modules each generating or absorbing heat due to conduction, the plural rows of modules being connected together in parallel between a first and a second power terminals for conduction; detection circuits provided for each row of modules and connected between an intermediate terminal provided in the middle of the row and one of the power terminals to detect a change in voltage between the power and intermediate terminals caused by an open circuit; and an alarm circuit common to each row of modules and activated to output an alarm when one of said detection circuits detects a change in voltage.

2. A detection apparatus according to claim 1 wherein: each of said detection circuits includes a switching element that conducts when power is turned on, a first control element that controls the switching element, and a second control element that detects a change in voltage between said power and intermediate terminals caused by an open circuit, in order to activate the first control element, wherein: said alarm circuit includes a third control element that activates an alarm generating means and a fourth control element that controls the third control element, and wherein: the switching elements in said detection circuits are connected together in series and further connected to the fourth control element in the alarm circuit so that if any switching element is opened, the fourth control element is activated to operate the third control element, thereby operating the alarm generating means.

3. A detection apparatus according to claim 2 wherein said alarm circuit includes a delay circuit for delaying the activation of the third control element by a specified period of time after the activation of the fourth control element.

4. A detection apparatus according to claim 1 wherein a diode bridge is incorporated between said power and intermediate terminals to absorb a change in the polarity of the applied voltage.

5. A detection apparatus according to claim 2 wherein said switching element is a photo coupler, wherein the first, third, and fourth control elements are transistors, and wherein the second control element is a Zener diode.

6. A detection apparatus according to claim 2 wherein a thermostat that is opened upon detecting a change in temperature is connected between the fourth control element and a row of switching elements comprising the switching elements in said detection circuits connected together in series.

7. A detection apparatus according to any of claims 1 to 6 including a malfunction prevention circuit for receiving a control signal that turns said thermo module on and off, and when the signal indicates an off state, disabling said alarm circuit by synchronizing with the signal.

8. A detection apparatus according to claim 7 wherein said malfunction prevention circuit includes a fifth control element connected to open and close part of the alarm circuit, and a switching element connected to the fifth control element such that during the input of said control signal, the switching element conducts to keep the fifth control element conducting, whereas while the control signal is not input, the switching element does not conduct to prevent the fifth control element from conducting.

9. A detection apparatus according to claim 8 wherein said fifth control element is a transistor and wherein the switching element is a photo coupler.